The following is an explanation of a molding of the prior art using a belt line molding installed in the belt line as the example. As shown in FIG. 7, a window is installed in the door 1 of an automobile. The door glass 2 is installed between a door outer panel 3 and a door inner panel (not shown) allowing the door glass to be raised and lowered. A belt line molding 10 is installed at the upper edge (belt line) of the door outer panel 3 at the bottom end of the window opening. The belt line molding 10 is molded using resin extrusion molding. If necessary, some metal plate components can be used as insert components or decorative components.
FIG. 8(A) shows the portion adjacent to the end of the resin extrusion-molded belt line molding 10 as viewed from the door outer panel attachment side, and FIG. 8(B) is a side view from the end cap side. FIG. 9 is a cross-sectional view of FIG. 8(A) from 9-9. A fitting portion 12a on the end cap 12 is inserted from the opening in the end surface of the molding main unit 11 of the belt line molding 10. Assembly holes are opened using a drill from the molding main unit 11 side in the main unit side 11a and the end cap side 12b so that there is no gap between the molding main unit 11 and the end cap 12.
A resin pin 13 extrusion-molded at the same time as the end cap 12 is cut from the end cap 12, and the resin pin 13 is inserted into the assembly holes 11a, 12b to keep the end cap 12 from coming off the molding main unit 11.
In the belt line molding 10 in FIG. 7 through FIG. 9, the process employed to keep the end cap 12 from coming off the molding main unit 11 requires a step in which assembly holes 11a, 12b are opened up, and a step in which a resin pin 13 is inserted into these assembly holes 11a, 12b. 
Thus, equipment is needed to open the hole in the molding main unit 11 and the end cap 12, and equipment is needed to insert the resin pin. The prior art also requires a great amount of assembly time.